The purpose of an audio loudspeaker system is the accurate generation of acoustic waveforms. This is accomplished by optimizing the speaker device as well as the associated enclosure.
It is known that when a speaker diaphram moves back and forth, audio waves are generated in both a forward direction from the speaker, and in a rearward direction to locations inside the enclosure. The rearward directed waves are 180.degree. out of phase with the forward directed waves.
In conventional speaker enclosures, the rearward directed waves generate acoustical distortions in several ways. That is, these waves can be reflected internally within the speaker enclosure and in a forward direction where they interfere with the operation of the speaker diaphram.
Acoustical distortion is also produced by the back and forth movement of the speaker diaphram which transmits vibrations through the speaker frame to the enclosure. The resulting resonance of the enclosure walls can generate waves which produce the audio distortion.
A number of conventional loudspeakers have been disclosed. For example, in U.S. Pat. No. 4,157,741 by Goldwater, there is disclosed a speaker system which includes a phase plug which minimizes audio distortion due to phase differences between waves generated by the speaker diaphram by equalizing wave path lengths between various portions of the diaphram and an exponential output horn of the speaker system.
In Mitchell, U.S. Pat. No. 4,235,301, there is disclosed a loudspeaker enclosure which is configured to channel soundwaves emitted from a back surface of a driver speaker so that the soundwaves are shifted in phase and emerge from a port in the speaker enclosure so as to add to the soundwaves emitted from the front surface of the speaker.
Another loudspeaker enclosure which is configured so as to direct rearwardly emitted soundwaves toward the front to combine with, and reinforce the tones emitted from the front of the speaker, is disclosed in U.S. Pat. No. 2,491,982 by Kincart.
Various configurations of speaker enclosures have also been disclosed. For example, in U.S. Pat. No. 4,142,604 by Smith and U.S. Pat. No. 4,280,586 by Petersen, there are disclosed enclosures having pyramidal configurations. Furthermore, in U.S. Pat. No. 4,073,365 by Johnson, there are disclosed speaker enclosures having hexahedronal and tetrahedronal configurations, respectively. Additionally, in U.S. Pat. No. 4,231,446 by Weiss et al, there is disclosed a speaker enclosure having a rhombic dodecahedron configuration.
Other internal configurations of speakers also have been disclosed. In Elworthy, U.S. Pat. No. 1,975,201, there is disclosed a structure located in the interior of a speaker enclosure which includes a number of intersecting walls which combine to produce a plurality of irregularly shaped cells to generate a number of deflected interference soundwaves.
Another loudspeaker enclosure which is divided internally into a number of intercommunicating compartments is disclosed by Forrester in U.S. Pat. No. 2,646,852. Furthermore, a speaker enclosure utilizing two balancing or equalizing chambers for discharging soundwaves into a single conduit for final discharge outwardly from the enclosure is disclosed in U.S. Pat. No. 3,263,769 by Mercurius.